This is a tricky one. On one hand, there's the obvious issues: almost everything you can talk about is societal or political. Talking about your lawn growing is societal because it means you can have a lawn and that gets into the housing crisis sooner or later. If people can't speak about politics, marginalized group will have difficulty bringing up tough issues that impact them in their day to day job.
On the other hand, I haven't seen a company where the various politics Slack channel didn't devolved to a couple of white guys in an eco chamber trashing anyone who isn't agreeing with their favorite issue of the day. And god forbid you're NOT part of that channel, because then you're the "one person who doesn't care" or some such. Some issues may be fairly one sided, at least at a high level (gender and race equality), others are much more nuanced (gentrification and housing, the school debt crisis) and the discussions are always bordering on needing HR involved to avoid people screaming at each other. Some are extremely subjective but just as heated in Slack (the whole working from home thing).
So how do you handle it? Let people talk about it but ban the slack channels? Ban it altogether? Have HR moderating the discussions? I honestly don't know. Right now it seems like the status quo of "let it happen and hope for the best" is the best of the bad options you have in front of you, but eventually something goes sour and you have to do something. Basecamp's approach is likely missing the mark, but I'd be curious what others are doing.
If your answer is "Nah, we have tons of political discussions at work and its all positives", you're probably not looking very hard.